Devices to compact parts out of powder material for sintering are well known to those persons skilled in the art. In some cases, the compacted part has an undercut which prevents removal of the part or blank from the dies by linear or axial displacement.
Tool sets with split dies are known in powder material compaction to press parts into shapes that have an undercut in the compacting direction.
For example, U.S. Pat. No. 3,773,446 teaches a device for moulding parts to be sintered by compressing powdered material held between a fixed die and moveable die. A pair of punches extending through the dies compresses the powder material. A pressure plate operated by the punch extending through the moveable die engages the moveable die and is also locked to the fixed die during the compression to produce a part having an undercut.
U.S. Pat. No. 3,752,622 teaches a device for moulding blanks with undercut parts to be sintered by compaction of powder material.
The prior art teaches that both parts of the die are tied together while a feed box moves across the top of the dies for filling the cavity with powdered material. After compaction the upper part of the die moves away together with the top punch to eject the part.
One of the disadvantages of the known systems as referred to above relates to the fact that the upper part of the die has to be tied mechanically to the lower part of the die and the upper punch in an alternating mode, thus making a complicated tool rig necessary.
Moreover, gearsets and camsets, for example, are characterized by two levels of the same shape but phased to each other to comprise an undercut in the compacting direction. Such parts may be manufactured in known methods as referred to above with the disadvantages noted therein.
Another disadvantage of the prior art is that the undercut can only be indirectly filled thereby creating a section of lower density in the compacted part.
It is therefore an object of this invention to provide a device that is simpler to construct and more efficient to operate than heretofore known by the prior art.
It is another object of this invention to provide a tool system with a split die where both parts of the die remain tied to one part of the rig during the entire cycle.
It is a further object of this invention to provide a device and method to produce compact phased parts such as gears, cams and the like with less complicated tooling and more efficient fill of the undercut than presently available.
In a first aspect of the invention there is provided a tool set for a powder molding machine having a pair of die sets each having a die and a punch moveable relative thereto to define respective chambers, the die sets co-operable to place the chambers in communication and thereby to define a mold cavity, the punches being movable relative to one another in a direction parallel to a common axis to reduce the volume of the mold cavity and to compress powder therein, the dies being movable relative to one another in a plane normal to the common axis, independently of movement along the common axis, to displace the chambers relative to one another and to define a phased component in the mold cavity, and the dies being separable in the direction of the common axis to permit a molded component to be removed therefrom.
In one aspect of the invention the dies are movable in linear translation, one relative to the other, in the plane normal to said common axis. In another aspect of the invention the dies are movable in rotation, one relative to the other, in said plane normal to the common axis.
In another aspect of the invention, the tool set is additionally movable to filling, transfer, lateral displacement and withdrawal positions and each said punch is at least partially engaged with each of said dies of said respective die sets in each of said filling, transfer, lateral displacement and withdrawal positions.
In still another aspect of the invention there is provided a tool set for mounting in a powder compacting press, the press having an axis of reciprocation, the tool set comprising a first die and punch set for mounting with the press, including a first die and a first punch movable within the first die to form a first chamber for receiving a charge of powder; a second die and punch set for mounting with the press, the second die and punch set co-operable with the first die and punch set and including a second die and a second punch movable within the second die for forming a second chamber therewithin; the second die movable parallel to the axis relative to the first die to meet the first die at an interface; and with the first and second dies in contact at the interface and with the first and second chambers in communication to define a closed mold cavity for containing the charge of powder, the second die being movable relative to the first die to a transversely displaced position.
Another aspect of the invention encompasses a press assembly for producing compacted powder metal parts, that press assembly comprising a powder press having an axis of reciprocation and a tool set for mounting in that press, that tool set including a first die set and a second die set, the first die set having a first die and a first punch movable in sliding engagement with, and relative to, the first die for forming a first chamber, the second die set having a second die and a second punch movable in sliding engagement with, and relative to, the second die for forming a second chamber, the die sets co-operable to place the chambers in communication and thereby to define a mold cavity, the punches being movable relative to one another in a direction parallel to the axis to reduce the volume of the mold cavity and to compress powder therein, the dies being movable relative to one another in a plane normal to the axis independently of movement along the axis to displace the chambers relative to one another and to define a phased component in the mold cavity, and the dies being separable in the direction of the common axis to permit a molded component to be removed therefrom.
One aspect of the invention is a method for making compacted powder parts with a tool set for mounting in a press having an axis of reciprocation, the tool set including a first die and punch set mountable in the press and a co-operating second die and punch set mountable in the press, the first die and punch set including a first die and a first punch movable therewithin to form a first chamber, the second die and punch set including a second die and a second punch movable therewithin to form a second chamber, that method comprising the sequential steps of a) establishing the tool set in a position in which the first chamber and the second chamber are in communication to form a closed mold cavity, with a charge of powder captured therein; b) displacing the second die relative to the first die while maintaining the first and second chambers in closed communication; c) compacting the powder to form a compacted powder part; and d) ejecting the compacted powder part from the tool set, in one embodiment of the invention the step of displacing includes linearly translating the second die relative to the first die. In another embodiment of the invention the step of displacing includes rotating the second die relative to the first die about an axis parallel to the axis of reciprocation. In yet another embodiment of this aspect of the invention step (a) includes a(i) filling the first chamber with the charge of powder; and a(ii) transferring a portion of the charge of powder from the first chamber to the second chamber.